The stock '66 AC engine I own had the 95 HP heads and no copper spacers under the cylinders as Bob said. Bob In a message dated 5/30/2012 4:00:05 P.M. Eastern Daylight Time, BobHelt at aol.com writes: !964 110 hp engines had 110 hp heads. Only 1965-67 RK 110 hp engines used the 95 hp heads. Regards, Bob Helt